One 32bit Port versus Four 8bit Ports

LoopyByteloose

I was looking at documentation for another 32-bit processor in order to have some idea of what 32 bit means.··I noticed that they have provided·4· single byte width ports while the Propeller has one 32 bit wide port.· Quite a departure from other RISC architectures.

To me it seems a·little difficult to·visualize how·one pin·of the Port A will be clocking an EEPROM, another pin will be Bit banging data from the EEPROM, a few more pins with be handling Chip select, AND other functions [noparse][[/noparse]such as video and a key board interface] will be working off of other pins which are all on this one and only Port.







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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Paul Baker

Because each cog has its own datain, dataout and pin direction registers. The direction and output value is by unanimous rule, any cog specifies a particular pin is output it's output, when a pin is an output any cog which states its a level high, its level is high. So for a pin to be input, all cogs must agree its input, for an output pin to be low, all cogs must agree its low.

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1+1=10

Tracy Allen

Also, both pasm and Spin have powerful masking instructions that direct the effect of command to single pins or to groups of pin. Groups do not necessarily have to be organized on the traditional boundaries of 1, 2, 8, 16. For example,
dira[noparse][[/noparse]17] := 1
outa[noparse][[/noparse]17] := 1
outa[noparse][[/noparse]13..15] :=0
affect the the named pins only. The one addressed to p17 would certainly make p17 a high output, no matter what other cogs have done to it previously. The command addressed to p13 to p15 would make those pins low, only if somewhere else they had been made outputs, and provided no other COG had set those pins high in its output register.

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Tracy Allen
www.emesystems.com

LoopyByteloose

Well, between the Masking instructions and the separate In and Out ports, I begin to see how different the concept is and why it works.
Thanks, I'll have to take another look at the docs and the Assember instructions [noparse][[/noparse]I see there are some 70plus compared to the SXes 40 or so].

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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Post Edited (Kramer) : 4/9/2006 4:11:04 PM GMT